SKELETAL SYSTEM
SKELETAL SYSTEM
• THE STRUCTURES OF THE SKELETAL
• SYSTEM INCLUDE:
• BONES, JOINTS, AND LIGAMENTS.
SKELETAL SYSTEM
• FUNCTIONS OF THE SKELETAL
SYSTEM
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5.
SUPPORT
PROTECTION
MOVEMENT
MINERAL STORAGE
BLOOD CELL FORMATION
CLASSIFICATION OF BONES BY
POSITION
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THE 206 BONES OF THE HUMAN
BODY ARE GROUPED INTO
THE AXIAL AND THE
APPENDICULAR SKELETONS.
AXIAL SKELETON
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THE AXIAL SKELETON
FORMS THE LONG AXIS OF THE
BODY AND INCLUDES THE
BONES OF THE SKULL, VERTEBRAL
COLUMN, AND THE RIB CAGE.
AXIAL SKELETON
• GENERALLY THESE BONES ARE MOST
• INVOLVED IN PROTECTING, AND
• SUPPORTING.
AXIAL SKELETON
AXIAL SKELETON
AXIAL SKELETON
AXIAL SKELETON
AXIAL SKELETON
AXIAL SKELETON
APPENDICULAR SKELETON
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THE APPENDICULAR SKELETON
CONSISTS OF THE BONES OF THE
UPPER AND LOWER LIMBS,
AND THE GIRDLES THAT
ATTACH THE LIMBS TO THE
AXIAL SKELETON.
APPENDICULAR SKELETON
• THE APPENDICULAR SKELETON
• CONSISTS OF 126 BONES. IT
• FUNCTIONS TO HELP IN MOVEMENT.
APPENDICULAR SKELETON
AXIAL and APPENDICULAR
SKELETONS
CLASSIFICATION OF BONE BY
SHAPE
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THE BONES OF THE HUMAN
SKELETON COME IN MANY SIZES
AND SHAPES. BONES CAN BE
CLASSIFIED BY SHAPE INTO:
LONG; SHORT; FLAT; IRREGULAR.
LONG BONES
Long bones are longer
than they are wide.
Long bones have 2
epiphyses, and a
diaphysis.
All of the bones of
the limbs, except the
patella, ankle, and
wrist, are long bones.
SHORT BONES
Short bones are
cube shaped, nearly
equal in length and
width.
The bones of the
wrist and ankle are
examples of short
bones.
SHORT BONES
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A SPECIAL TYPE OF SHORT
BONE IS A SESAMOND BONE.
THIS TYPE OF BONE IS A
SHORT BONE WHICH FORMS
WITHIN A TENDON. AN EXAMPLE
IS THE PATELLA, AND THE PISIFORM.
FLAT BONES
Flat bones are thin,
flattened, and a bit
curved.
The sternum,
•scapulae, ribs, and
most of the bones of
the skull are flat bones.
IRREGULAR BONES
Irregular bones have
•complicated shapes
that fit none of the
preceding classes.
The vertebrae, the
bones of the hip, and
some facial bones.
GROSS ANATOMY OF A
LONG BONE
A long bone has a
shaft, the Diaphysis,
and two ends,the
epiphyses.
Covering a long bone
in all area, except the
•articular surfaces, is
•Periosteum.
GROSS ANATOMY OF A
LONG BONE
Covering the articular
surfaces is articular,or
hyaline, cartilage.
Deep to the periosteum
•is a layer of compact
bone.
•this layer is thicker in the
•diaphysis than the
•epiphysis.
GROSS ANATOMY OF A
LONG BONE
In the diaphysis of
•the long bone deep to
the compact bone is
•the medullary cavity.
•in an adult it is full of
•yellow bone marrow.
The medullary cavity
•is lined with endosteum.
GROSS ANATOMY OF A
LONG BONE
In the epiphyses deep
to the layer of compact
bone is spongy bone.
 Between the
•trabecula of the spongy
bone is red bone marrow.
GROSS ANATOMY OF A
LONG BONE
MICROSCOPIC STRUCTURE
OF COMPACT BONE
• THE STRUCTURAL UNIT OF
• COMPACT BONE IS THE OSTEON,
• OR HAVERSIAN SYSTEM. EACH
OSTEON
• IS AN ELONGATED CYLINDER
• ORIENTED PARALLEL TO THE
• LONG AXIS OF THE BONE.
MICROSCOPIC STRUCTURE
OF COMPACT BONE
MICROSCOPIC STRUCTURE
OF COMPACT BONE
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AN OSTEON IS A GROUP OF HOLLOW
TUBES OF BONE MATRIX,
ONE PLACED OUTSIDE THE NEXT
LIKE THE GROWTH RINGS OF A
TREE TRUNK. EACH OF THE MATRIX
TUBES IS A LAMELLA.
MICROSCOPIC STRUCTURE
OF COMPACT BONE
• THE COLLAGEN FIBERS IN A
• PARTICULAR LAMELLA RUN IN
• A SINGLE DIRECTION.
MICROSCOPIC STRUCTURE
OF COMPACT BONE
MICROSCOPIC STRUCTURE
OF COMPACT BONE
Running through the
core of each osteon is
the central,or Haversian
canal.
 The canal contains
small blood vessels and
nerve fibers that serve
the needs of the
osteon’s cells.
MICROSCOPIC STRUCTURE
OF COMPACT BONE
Spider shaped osteocytes
occupy small cavities called
lacunae at the junctions of
the lamellae.
Hair like canals called
•canaliculi connect the
•lacunae to each other.
The space between these
•structures is occupied by
bony matrix.
MICROSCOPIC STRUCTURE
OF COMPACT BONE
GROSS ANATOMY OF
FLAT BONE
OSSIFICATION
• OSSFICATION OR OSTEOGENESIS
• IS THE PROCESS OF BONE
FORMATION.
• THERE ARE 2 MECHANISM
• WHICH FORM BONE:
• 1. INTRAMEMBRANOUS
• 2. ENDOCHONDRAL
OSSIFICATION
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INTRAMEMBRANOUS OSSIFICATION
RESULTS IN THE FORMATION
OF THE CRANIAL BONES AND
THE CLAVICLES.
OSSIFICATION
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ENDOCHONDRAL OSSIFICATION
RESULTS IN THE FORMATION OF THE
BONES BELOW THE
SKULL, WITH THE EXCEPTION OF
THE CLAVICLES.
OSSIFICATION
• THREE TYPES OF CELLS ARE
INVOLVED
• IN BOTH MECHANISM OF
OSSIFICATION:
• 1. OSTEOBLASTS
• 2. OSTEOCLASTS
• 3. OSTEOCYTES
STEPS OF INTRAMEMBRANOUS
OSSIFICATION
•1. Selected
mesenchymal cells
•cluster and form
osteoblasts.
•2. This forms an
ossification center.
STEPS OF INTRAMEMBRANOUS
OSSIFICATION
•3. Osteoblasts begin
to secrete osteoid,
which mineralized.
•4. The osteoblasts
are trapped
differentiate into
osteocytes.
STEPS OF INTRAMEMBRANOUS
OSSIFICATION
•5. Accumulating
osteoid is laid down
between embryonic
blood vessels.
•6. This forms a
network of trabulae.
STEPS OF INTRAMEMBRANOUS
OSSIFICATION
•7. Vascularized
mesenchyme condenses
on the external face
•of the woven bone and
becomes the periosteum.
STEPS OF INTRAMEMBRANOUS
OSSIFICATION
•8. Trabeculae just
deep to the periosteum
thicken, forming a bone
collar.
•9. The bony collar is
later replaced with
mature compact bone.
STEPS OF INTRAMEMBRANOUS
OSSIFICATION
•10. Spongy bone,
consisting of distinct
trabeculae, are present
•internally. Blood
vessels
•differentiate into red
bone marrow.
STEPS OF ENDOCHONDRAL
OSSIFICATION
•1. The perichondrium
covering the hyaline
cartilage “bone” is
infiltrated with blood
•vessels.
•2. Osteoblasts secrete
osteoid against the hyaline
cartilage diaphysis,
encasing it in a bony collar.
STEPS OF ENDOCHONDRAL
OSSIFICATION
•3. Chondrocytes
within the diaphysis
hypertrophy and signal
the surrounding
cartilage matrix to
calcify.
•4. The chondrocytes,
however, die and the
matrix begins to
deteriorate.
STEPS OF ENDOCHONDRAL
OSSIFICATION
•5. In month 3, the
forming cavities are
invaded by a collection
of elements called the
periosteal bud.
•6. The entering
osteoclasts partially
erode the calcified
cartilage matrix.
STEPS OF ENDOCHONDRAL
OSSIFICATION
STEPS OF ENDOCHONDRAL
OSSIFICATION
•7. Osteoblasts
secrete osteoid around
the remaining
fragments of hyaline
cartilage forming
trabeculae.
STEPS OF ENDOCHONDRAL
OSSIFICATION
•8. As the primary
ossification center
enlarges, osteoclasts
break down the newly
formed spongy bone
and open up a medullary
cavity in the center of
the diaphysis.
STEPS OF ENDOCHONDRAL
OSSIFICATION
•9. The epiphyses remain
formed of cartilage until
shortly before or after
birth.
•10. Secondary
ossification centers form
in the epiphyses. The
events of ossification are
like the events of the
diaphysis, except, that
spongy bone mains in the
internal and no medullary
cavity forms.
STEPS OF ENDOCHONDRAL
OSSIFICATION
STEPS OF ENDOCHONDRAL
OSSIFICATION
BONE GROWTH
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THERE ARE 2 TYPES OF
BONE GROWTH:
1. LONGITUDINAL--LENGTH
2. APPOSITIONAL--DIAMETER
Epiphyseal
plate
LONGITUDINAL BONE GROWTH
Osteoblast
APPOSITIONAL BONE GROWTH
BONE GROWTH
CALCIUM HOMEOSTASIS
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FACTORS OF CALCIUM
HOMEOSTASIS:
1. HORMONES
2. VITAMIN D—MILK
3. CALCIUM—MILK
4. VITAMIN A—CARROTS
5. PHOSPHORUS—MEAT
HORMONAL CONTROL OF
CALCIUM HOMEOSTASIS
CALCIUM HOMEOSTASIS
• OTHER FACTORS IN CALCIUM
• HOMEOSTASIS:
• 1. VITAMIN D—AIDS IN THE ABSORPTION
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OF BOTH CALCIUM AND PHOSPHORUS.
• 2. VITAMIN A—HELPS THE OSTEOBLASTS
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PRODUCE BONY MATRIX.
CALCIUM HOMEOSTASIS
• 3. TESTOSTERONE AND ESTROGEN—
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STIMULATES BONE DEPOSITION OF
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CALCIUM STARTING AT PUBERTY.
HOMEOSTATIC IMBALANCES OF
THE SKELETAL SYSTEM
• RICKETS
• 1. DISEASE OF CHILDREN DUE TO
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LACK OF VITAMIN D.
• 2. CALCIUM IS NOT DEPOSITED.
• 3. BOWING OF THE BONES.
HOMEOSTATIC IMBALANCES OF
THE SKELETAL SYSTEM
• OSTEOMALCIA
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1. RICKETS IN ADULTS
2. DUE TO A LACK OF VITAMIN D
3. CALCIUM IS NOT DEPOSITED IN
BONE.
4. MAIN SYMPTOM IS PAIN WHEN WEIGHT
IS PUT ON THE AFFECTED BONE.
HOMEOSTATIC IMBALANCES OF
THE SKELETAL SYSTEM
• OSTEOPOROSIS
• 1. BONE REABSORPTION IS GREATER
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THAN BONE DEPOSITION.
• 2. CAUSES:
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A. LACK OF ESTROGEN
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B. LACK OF EXERCISE
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C. INADEQUATE INTAKE
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D. LACK OF VITAMIN D
HOMEOSTATIC IMBALANCES OF
THE SKELETAL SYSTEM
• OSTEOPOROSIS
• 3. SIGNS AND SYMPTOMS:
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A. SPONGY BONE OF THE SPINE IS MOST
VULNERABLE.
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B. OCCURS MOST OFTEN IN
POSTMENOPAUSAL WOMEN.
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C. BONES BECOME SO FRAGILE THAT
SNEEZING OR STEPPING OFF A CURB CAN CAUSE
FRACTURES.
• 4. TREATMENT
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A. CALCIUM AND VITAMIN D SUPPLEMENTS.
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B. HORMONE REPLACEMENT TREATMENT
C. INCREAE WEIGHT BEARING EXERCISE.
HOMEOSTATIC IMBALANCES OF
THE SKELETAL SYSTEM